Coal flotation process



Patented Jan. 2a, 1936- PATENT OFFICE COAL FLOTATION PROCESS Philip M. Franta, Pueblo, Colo., assignor to The Colorado Fuel and Iron Company,

Colo.

Denver No Drawing. Application January 12, 1932, Serial No. 586,250

- 15 Claims.

This invention relates to a process for the recovery of coal from coal and'water pulps by what is commonly known as flotation.

In the flotation process as usually practised,

5 finely divided matter suspended in liquid is sub- Jected to a treatment which causes coal-particles present in the pulp to rise to the surface of the liquid, for their discharge across an overflow.

The treatment consists in the agitation and/or aeration of the pulp in the presence of a reagent which promotes separation of coal particles which entrapped in air-globules, rise to the liquid-surface in the form of a froth, from gangue-particles which are wetted and settle out of the liquid mass.

The present invention resides more particularly in the nature of the reagent and in the method of mixing it with a coal-water pulp in a flotation process, and its principal object is to provide by the use of a simple and highly eflicient reagent of novel character, a process in which a substantially clean separation of coal-particles in aqueous suspension, from extraneous matter is readily effected.

Another object of the invention is to'produce in a process of the above described character, a clean product with a minimum content of ash and/or sulphur, thereby insuring the recovery of coal which would otherwise be lost.

A further object resides in providing a reagent capable of floating a given amount of coal in the pulp under treatment, thereby permitting very close control of the flotation operation by adding the reagent to the pulp progressively in quantities proportionate to the coal content of the same. A further object of the invention resides in the provision of a method of applying the reagent to the pulp, whereby to insure its effect upon the coal-content thereof to the full extent of its reactive capacity.

Still another object is to provide a reagent for use in the recovery of coal by flotationwhich has all the desirable qualtities mentioned above, and in'additlon is cheap and easily obtained.

45 It is to be understood that my invention relates exclusively to a process for the recovery of coal, not to be confounded with the well known flotation processes for the treatment of sulphide and oxide ores.

Best results are obtained by first mixing the The reagent produced in accordance with the.

petroleum and kerosene by stirring or other means of agitation, then allowing it to stand for about fifteen minutes, and adding the creosote to the mixture immediately before or during its use in the process. 5

A coal tar creosote having a specific gravity of 1.05.4, a boiling point of 210 centigrade and a solid residue of 18% to 19% at 355 centigrade is well adapted for the purpose, particularly in the recovery of bituminous coal. 10

While the amount of creosote added to the petroleum-kerosene mixture may be varied in accordance with different conditions and different characteristics of the material to be treated, it has been found that from 3% to 5% of creosote 15 added to from 95% to 97% of the crude oil-kerosene mixture produces highly satisfactory results. It is desirable that the creosote be added to the pulp with the mixture of crude oil and kerosene, or shortly after the mixture has been intro- 20 duced into the pulp, it having been found that if the creosote is added first, the results are erratic.

The amount of reagent to be used to a given amount of material depends on the amount of coal in the pulp, or in other words, on theamount 25 of coal recoverable by flotation.

The amount of the reagent necessary to treat a ton of coal, will, under ordinary conditions, not exceed one gallon or about eight pounds. In fact, excellent results have been obtained by the use 30 of as low as five pounds of reagents per ton of coal.

A simple method of applying the reagent to the pulp'consists in using aso-ealled conditioning machine as a means for mixing the reagent with 35 the pulp before it enters the flotation machine.

The flotation machine may be of any desired construction, and of single or multiple cell type. In a machine of the last-mentioned type, the pulp is caused to flow successively from one cell to another, each cell yielding a clean froth of coal which is removed as soon as it is formed. Since machines of this character are well known in the flotation art, it is thought to be unnecessary to describe them in detail or to exemplify the same by illustration. As stated hereinbefore, close control of the flotation process is one of the principal objects of the invention. The amount of the above described reagent to be used in the process is directly proportionate to a given amount of material under treatment, or stated in another way, one pound of reagent will float just so many pounds of coal and no more.

After the reagent has performed its function upon the given amount of material. reaction to continue the process. The process in order to produce satisfactory results, therefore, requires the gradual addition of reagents in quantities regulated according to the coal content of the Pulp.

In this manner violent disturbance, detrimental to the clean separation of the coal from the gangue is avoided, and a much cleaner coal is produced than would otherwise be possible. .By adding'but a small amount of the reagent at the beginning, and then maintaining the reaction at a constant level by adding other small quantities of the reagent gradually tapering down in proportion to the diminishing coal content of the material, the process is at all times under close control, and the maximum amount of coal will be floated without losses by violent or over-reaction, and with the expenditure of the minimum amount of reagent. A clean separation of the coal-content of the pulp with a maximum recovery,- is thus assured.

In the use of a multiple-cell flotation machine, it is preferred to add the reagent to alternate cells, starting with the second cell, after the pulp with a small quantity of the-reagent. has been fed to the first cell of the series from the conditioning machine.

In the present process, if all of the reagent re-, quiredwere added to the material in the conditioning machine, the reaction in the first cell would be so violent and the froth would be so dense, that fine ash would be-entrained.

f obviouslyis a condition which woulddefeat the main object of the invention.

Distinctive features of the process conducted in accordance with the present invention are that it requires no critical temperature to be maintainedto insure good results; that it is adapted for the treatment of slightly acid or alkaline pulps as well as neutral pulps and that long exposures to the atmosphere does not aifect the emciency of the reagent. The use of a reagent that is active in small quantities until its reactive function has been performed, gives the close control which, as stated before, is one of the main objects of the invention. The reagent of the present invention differs in this respect from other reagents used in the flotation process, and it is this characteristic of the reagent that insures the recovery of practically all of the coal in the material with a minimum content of ash, sulphur or other extraneous matter, in one.

. operation.

. Having thus described the reagent and the method of using the same, it will be apparent that variations and changes in the proportions of the constituents of the reagents and in the process of applying the same to the pulp, may be resorted to within the scope of the invention. V For example, the quality of the coal product obtained in the treatment of different coal and water pulps by the process, may be closely controlled by varying the proportionate amounts of 2. Iri a process of recovering coal from a coal and. water pulp, by. froth flotation, the step of adding to the coal pulp while the process is in progress, a reagent in progressively decreasing amount of coal in the pulp, said reagent consisting solely of-a mixture of crude paraffin base petro- I leum oil, kerosene and coal tar creosote.

3. In a process of recovering coal from a coal and water pulp, by froth flotation, the step of adding to the coal pulp a mixture consisting solely of crude parafiin base petroleum oil and kerosene, and coal tar creosote.

4. In a process of recovering coal from a coal and water pulp, by froth flotation, the step of adding to the coal pulp a mixture of a crude paraflin base petroleum oil and kerosene and then adding coal tar creosote.

5. In a process of recovering coal from a coal and water pulp, by froth flotation, the step of adding to the coal pulp, while the process is in progress, a reagent in quantities progressively decreasing in ratio to a gradual'decrease in the coalcontent of the pulp, said reagent consisting solely of a mixture of crude parafiin base petroleum oil, kerosene and coal tar creosote.

6. The process of recovering coal from a coal and-water pulp, by froth flotation, comprising adding to the coal pulp in the presence of agitation and aeration, a mixture consisting solely of .solely of crude paraffin petroleum oil and kerosene, and coal tar creosote.

8. The step of the process according to claim 3, in which is used coal tarcreosote having a specific gravityof 1.054, a boiling point of 210 centigrade and a solid residue of 18% to 19% at 355 centigrade.

9. ma process of recovering coal from a coal and-wa'ter pulp, by froth flotation, the steps of adding to the coal pulp a mixture of crude paraflin base petroleum oil and kerosene 95% to97% and adding coal tar creosote to'3%.

10. In a process of recovering coal from a coalandwater'pulp in a multiple-cell froth flotation machine, the steps of adding to the coal pulp in alternate cells of the machine, a mixture consisting solely of crude paraflin base petroleum oil and kerosene, and coal tar creosote.

- 11. In a process of recovering coal from coaland water pulp in a frothfl'otation treatment. the step of subjecting coal pulp to. a flotation reaction product produced bythe simultaneous presence of a mixture consisting solely of crude paraflin base oil, kerosene and coal tar creosote.

12. In a coal froth flotation process comprising treatment of coal and water pulp in successive stages in each of which there is a removal of coal floated under the influence of a reagent, the steps of adding a reagent to the coal pulp in said stages, in separate quantities proportionate to the coal content of the pulp body in the respective stages, whereby to compensate progressively for the quantities of the reagent removed from the pulp bodywith the floated coal, said reagent consisting solely of a mixture of crude, paraflln base petroleum oil, kerosene and coal tar' creosote.

13. The method 'of controlling a coal 'iroth flotation process according to the maximum of coal in the pulp in aseries of treatments,

whereby the maximum amount of coal which the reagent is capable of floating, is'floated at each stage of the treatment, said reagent consisting solely of a mixture 01' crude parafiin base petroleum oil, kerosene and coal tar creosote.

14. The method of treating coal by flotation comprising subjecting the coal to a froth flotation process in the presence of a flotation agent comprising predominating quantities of kerosene and crude paraflin base petroleum oil-and a minor portion of coal tar creosote, the kerosene functioning to speed up the collecting action of the cmde oil and stabilizing the frothing action of the creosote.

15. The method of treating coal by flotation comprising subjecting the coal to a froth flotation process in the presence of a flotation agent comprising kerosene, crude parafiin base petroleum oil and coal tar creosote, the kerosene and crude oil predominating in the mixture and being present in approximately equal quantities the kerosene functioning to speed up the collecting action of the crude oil and stabilizing the frothing action of the creosote.

PHILIP M. FRANTZ. 

